I have restarted my local nginx and the php5-fpm service several times after confirming the extension is there, but with no result. Can somebody offer any suggestions on how I can proceed? Thanks!phpinfo

this is what happened on my Linux Mint Qiana distro:
the phalcon ./install script automatically created a hardcoded ini file in /etc/php5/fpm/conf.d whereas the available ini files are normally stored in /etc/php5/mods-available and then symlinked to the appropriate conf.d folders. Therefore the extension was available to the php5-fpm process but not to the php-cli executable.

Fix:
move the ini to the mods-available folder and create appropriate symlinks to /etc/php5/fpm/conf.d as well as /etc/php5/cli/conf.d folders

This is needed in Ubuntu/Mint

On my VPS where I have Debian 7, the /etc/php5/fpm/conf.d folder is symlinked in its entirety to the conf.d from the cli folder. In that case a symlink or hard file in that folder just works.